An air conditioner includes a refrigeration cycle configured by sequentially disposing, in a refrigerant circulation channel in which a refrigerant is enclosed, a compressor that compresses the refrigerant, an indoor heat exchanger that causes the refrigerant and the indoor air to perform heat exchange, an expansion valve that decompresses the refrigerant, and an outdoor heat exchanger that causes the refrigerant and the outdoor air to perform heat exchange. The outdoor heat exchanger is housed in a housing of an outdoor unit together with a fan that sends the air to the outdoor heat exchanger. The indoor heat exchanger is housed in a housing of an indoor unit together with a fan that sends the indoor air to the indoor heat exchanger.
As a form of the outdoor unit, there are, for example, an upper blowing type for blowing the air after the heat exchange from an upper part of the housing and a lateral blowing type for blowing the air after the heat exchange from the front surface of the housing. As the indoor unit, there are various forms according to installation places. In recent years, in particular, in the business field, a ceiling embedded cassette type for embedding a housing in the ceiling and performing suction and blowout of the air via a decorative panel set on the ceiling surface is mainly used. A sectional view of an indoor unit of a conventional air conditioner is shown in FIG. 7. The indoor unit is configured from a decorative panel 101 and a housing 102 connected to the decorative panel 101. The decorative panel 101 includes a suction grill 103 in the center. An outlet 105 including a wind directing plate 104 is disposed around the decorative panel 101. A centrifugal fan 121 consisting of a motor 106 and a fan member 107 connected to a shaft 120 of the motor 106 is set in the housing 102. The motor 106 is operated, whereby the fan member 107 rotates. As indicated by an arrow 115 in FIG. 7, the indoor air is sucked into a suction port 112 of the fan member 107 through the suction grill 103, a filter 116 set in the suction grill 103, and a bell mouth 110 set in the housing 102 and is discharged from a discharge port 113 of the fan member 107 as indicated by an arrow 118. An indoor heat exchanger 108 is disposed to surround the centrifugal fan 121. The air discharged from the fan member 107 is subjected to heat exchange in the indoor heat exchanger 108 and thereafter blown out into a room from the outlet 105 as indicated by an arrow 117. A drain pan 109 for receiving dew condensation water caused in the indoor heat exchanger 108 during cooling is set below the indoor heat exchanger 108. The suction grill 103 is detachable from the decorative panel 101 together with the filter 116. This structure makes it easy to perform cleaning of the filter 116. An electrical component box 111, in which a not-shown control board for controlling the operation of the indoor unit is housed, is set on the lower surface of the bell mouth 110. This structure makes it possible to easily perform maintenance of the electrical component box 111 by opening the suction grill 103. The bell mouth 110 is attached to an inner circumferential part of the drain pan 109 from below. This structure makes it possible to easily perform maintenance such as replacement of the fan member 107 and the motor 106 by opening the suction grill 103 and detaching the bell mouth 110.
FIG. 8 shows a sectional view of the centrifugal fan 121 taken along a plane including a rotating shaft. A vibration prevention member 126, in which a rubber material 125 is joined by vulcanized adhesion between an inner cylinder 123 made of metal and an outer cylinder 124 made of metal, is attached to the center of the fan member 107. The inner cylinder is fit in the shaft 120 of the motor 106. By tightening a nut 127 over a screw provided at the distal end of the shaft 120, the motor 106 and the fan member 107 are fixed. FIG. 9 is a diagram of the vibration prevention member 126 viewed from the direction of the suction port 112 of the fan member. Both of a joining section of the inner cylinder 123 and the rubber material 125 and a joining section of the outer cylinder 124 and the rubber material 125 are circular. When the shaft 120 of the motor 106 rotates, a turning force is transmitted to the fan member 107 via the vibration prevention member 126. An electromagnetic exciting force generated by the motor 106 is absorbed and attenuated by the rubber material 125 to be prevented from being transmitted to the fan member 107. Occurrence of electromagnetic sound is suppressed. At this point, the turning force received by the vibration prevention member 126 acts as shearing stress in a rotating direction on adhesion interfaces between the inner cylinder 123 and the rubber material 125 and between the outer cylinder 124 and the rubber material 125. Further, downward shearing stress by the own weight of the fan always acts on the adhesion interfaces. Therefore, it is necessary to sufficiently secure shearing strength of the adhesion interfaces between the inner cylinder 123 and the rubber material 125 and between the outer cylinder 124 and the rubber material 125. However, in order to sufficiently secure the shearing strength, it is necessary to appropriately perform surface treatment of an outer circumferential section of the inner cylinder 123 or an inner circumferential section of the outer cylinder 124. Therefore, manufacturing cost is increased.
On the other hand, for example, in JP-A-11-62891, a large number of concaves and convexes extending in the axial direction are formed at a predetermined interval in the circumferential direction on the outer circumferential surface of the inner cylinder of the vibration prevention member. Consequently, a part of torque in the rotating direction acts as stress in a direction for compressing rubber. Therefore, it is possible to reduce stress in a shearing direction.